I read this book in 2001. It's a typical eco-horror story with a giant alligator in a swamp. Main character is a female (tour guide?) and the guy she doesn't get along with for most of the movie but ends up being her love interest is an alligator wrangler. Group of them along with some tourists to catch or see the alligator, alligator attacks, everyone is getting eaten one by one, etc. The part that stands out is one of them (I think the female) ends up in the alligator's den but manages to survive somehow. Very similar scene happened in the movie Rogue but the movie came out in 2007 and the Wiki page doesn't mention it being based on a book.